difference between CB,CE,CC transistor configurations

This page compares CB vs CE vs CC transistor configurations and mention difference between CB, CE, CC transistor modes. These modes are used in various transistor based applications as per characteristics mentioned below.

As we know transistor is solid state equivalent of a triode valve. It is a solid state, current gain device which has 3 terminals. The terminals are collector, base and emitter. It is made by both the p-type and n-type materials. Hence it is available in PNP and NPN configurations. It is referred as bipolar transistor.

There are three basic configurations of transistors viz. Common Base (CB), Common Emitter (CE) and Common Collector (CC) used in electronic circuits. Following are the important characteristics of these different modes or configurations. Based on these they are used for different applications. Figure-1 depicts all the three transistor configurations used in various applications of electronic circuit.

Transistor CB (Common Base) configuration

It is transistor circuit in which base is kept common to the input and output circuits.
Characteristics:
• It has low input impedance (on the order of 50 to 500 Ohms).
• It has high output impedance (on the order of 1 to 10 Mega Ohms).
• Current gain(alpha) is less than unity.

Transistor CE (Common Emitter) configuration

It is transistor circuit in which emitter is kept common to both input and output circuits.
Characteristics (applications):
• It has high input impedance (on the order of 500 to 5000 Ohms).
• It has low output impedance (on the order of 50 to 500 Kilo Ohms).
• Current gain (Beta) is 98.
• Power gain is upto 37 dB.
• Output is 180 degree out of phase.

Transistor CC (Common Collector) configuration

It is transistor circuit in which collector is kept common to both input and output circuits. It is also called as emitter follower.
Characteristics:
• It has high input impedance (on the order of about 150 to 600 Kilo Ohms).
• It has low output impedance (on the order of about 100 to 1000 Ohms).
• Current gain (Beta) is about 99.
• Voltage and power gain is equal to or less than one.

Following table summarizes important points about CB,CE,CC transistor configurations.

Parameter	Common Base	Common Emitter	Common Collector
Voltage Gain	High, Same as CE	High	Less than Unity
Current Gain	Less than Unity	High	High
Power Gain	Moderate	High	Moderate
Phase inversion	No	Yes	No
Input Impedance	Low (50 Ohm)	Moderate (1 KOhm)	High (300 KOhm)
Output Impedance	High (1 M Ohm)	Moderate (50 K)	Low (300 Ohm)

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